Recently, with development of information and communication technology, a variety of wireless communication technologies have been developed. Among such wireless communication technologies, a wireless local area network (WLAN) refers to technology for wirelessly accessing the Internet at home, at work or in a specific service provision area based on radio frequency technology using portable terminals such as personal digital assistants (PDAs), laptops, portable multimedia players (PMPs).
To overcome limited communication speed which has conventionally been a weak point of a WLAN, in the recent technical standard, a system for increasing the speed and reliability of a network and increasing the coverage of a wireless network has been introduced. For example, in IEEE 802.11n, multiple input multiple output (MIMO) technology using multiple antennas in a transmitter and a receiver in order to achieve high throughput (HT) of 540 Mbps or more, minimize transmission errors and optimize a data rate has been introduced.